1. Field of Invention
The present invention relates to valve stem seal assemblies for use in internal combustion engines, and more particularly to service tools adapted for removal of such assemblies from valve guides of engines.
2. Description of the Prior Art
Those skilled in the art will appreciate the manner in which intake and exhaust valves are employed in cylinder heads of internal combustion engines. Such valves, supported for reciprocal motion within valve guides, include integral elongated stems extending away from the engine cylinder heads, the ends of the stems typically interacting with rotating overhead cams for cyclic or repeated opening and closure of the valves against the force of valve return springs during the combustion cycle. Obviously, in order to permit unobstructed reciprocal movement of the stem in the guide, some mechanical clearance must exist between the valve guide and the moving stem. A plurality of valve stems thus move reciprocally to and from the cylinder head, each within its individual guide, and so-called valve stem seal assemblies are used to seal against leakage of oil through a mechanical clearance path between each annular engine valve guide and its associated valve stem.
As is well known, the intake port of a combustion chamber is opened and closed by the reciprocating motion of at least one intake valve, which in turn is driven by the rotary motion of a cam, the latter being affixed to and rotatable with an engine camshaft. The intake valve permits fuel mixed with air to flow into the combustion chamber. In addition, an internal combustion engine has at least one exhaust valve and associated exhaust port for releasing expended combustion gases to the atmosphere. Typically, intake and exhaust valves are of similar construction and both include stems integrally affixed to the valves.
In the typical engine, a valve stem seal assembly is fitted over or atop each valve guide, wherein each seal assembly has a typically cylindrical flangeless retainer frictionally mounted to an associated valve guide, or is alternately retained in place by a flanged retainer and having a normally bottom retainer flange that cooperates with a return spring to assure securement of the assembly on the valve guide under conditions of reciprocal movement of the valve stem within the guide. Each valve stem seal assembly normally has two primary parts; 1) an elastomeric oil seal engaging the valve stem to control leakage of oil between valve stem and guide as noted, and 2) a cylindrical retainer mounted atop of the valve guide to hold the oil seal in place. One particular design of the flangeless style of retainer includes a plurality of elongated fingers to frictionally hold the retainer in place on the guide. The seal is supported in the top of the retainer, and retainer fingers depend downwardly from a portion of the retainer below the elastomeric body of the seal. Radially inwardly extending ends of the fingers are circumferentially adapted to be retained by detents located in the valve guide circumference. Removal of such valve stem seal assemblies is rather cumbersome without an effective tool.
The service tool of the present invention overcomes normal difficulties of removal, and thus facilitates replacement of finger retainer-style valve stem seal assemblies during an engine overhaul.
The present invention provides a service tool for dislodgement and removal of valve stem seal assemblies installed atop valve guides of internal combustion engines. The service tool is particularly suited for flangeless retainers having elongated fingers circumferentially arranged for securement to the valve guide, wherein the guide includes detents for frictionally retaining inwardly turned ends of the fingers. In a preferred form, the service tool includes an exterior cylindrical shell formed in two symmetrical halves divided along the longitudinal axis of the shell. A cylindrical puller element is encased within and axially movable in the shell, the puller element also comprising two mating symmetrical halves divided along the same axis. The puller halves are hinged at their top end, and define gear teeth extending about their exterior upper surfaces, and radially inwardly turned arms at their lower ends. The puller arms comprise cam ends which include upwardly turned surfaces adapted to engage and dislodge circumferentially spaced fingers of the valve seal assemblies when the tool is circumferentially closed (i.e., via hinge) about an installed valve stem seal. Respective mating halves of puller and shell are coupled together in a manner to support axial vertical movement of the puller within the shell, and to permit the respectively mated halves to swing open together about the top hinge of the puller.
A pair of symmetrically opposed worm gears is supported in sockets of the exterior shell halves; one gear and socket are positioned in each half, wherein each worm gear respectively engages gear teeth of one of the puller halves. A pair of levers is disposed for angular up and down movement, wherein each lever is rigidly affixed to one respective worm gear, and extends radially outwardly therefrom. Simultaneous movement of said levers produces an angular follower movement of the worm gears within their respective sockets, causing the gear teeth of the worm gears to move in rotatably axially directed arcs, whereby the puller is caused to move up within the shell to dislodge the retainer fingers from their valve guide detents via the puller cam ends.